I would be interested in an answer to this
as well.
I finally will get my Librem 15 in the next days/weeks (it is on the way 
) and I’m one of the poor guys who have to deal with a UK layout now (instead of a German one which I ordered over a year ago and which was removed from possible settings in the meanwhile).
I thought about to use some kind of key covers or stickers but I did not really find something up to now. E.g. this
is a full cover for Mac Books so the quality might be ok, but as it is one cover for all keys, I probably have to cut out all the keys I want to cover and I don’t know how this will look like (I assume not very professional 
). If there is anyone out there who can suggest single key key covers/sticker so that I will still have an advantage of the backlight → feel free to share. Of course this is just a interims solution as long as there is no really keyboard available.
Looking at the pricetag of most keyboard out there in general I think an alternative keyboard layout feels like somehting which should be possible. I also think that most interested people in Germany/Switzerland/Austria would also pay some extra bugs for such a non default keyboard (in comparsion to the UK/US Purism currently offers).
Apart from that an e-Ink keyboard would be the most flexible and smartest solution. → An e-ink keyboard?